Packet communication system

ABSTRACT

The packet communication system enables communication between a communication unit connected in a conventional telephone network and a communication unit in a packet mode network. A device for exclusively selecting the connection network is provided so that, at the time of transmission of a signal from one communication unit to another, the connection path is selected according to the kind of the network to which the other communication unit belongs. At the time of signal reception, the communication unit is connected to only one of the conventional telephone network and the packet mode network. The packet communication system includes a packet processor for converting an information signal, such as speech, inputted from an input unit (for example, a transmitter microphone of a handset) into the form of a packet. The packet is transmitted to the packet mode network and converted into the original information signal stream to reproduce the signal stream by an output unit (for example, a receiver of the handset). A conventional telephone network interface controller is provided for reproducing the speech or like information signal received from the conventional telephone network by the output unit. An exclusive selector selects either the conventional telephone network or the packet mode network at the time of signal reception.

BACKGROUND OF THE INVENTION

This invention relates to a packet communication system used for packetmode communication of a signal, such as, an audio signal or a videosignal through a communication network, and more particularly to apacket communication system suitable for packet mode communication of asignal, such as, a speech signal between communication networks usingsignal types different from each other.

With the recent progress of the architecture of a LAN (local areanetwork), the network system connecting small size computers, such as,personal computers using the LAN is also increasing. Thus, an attempt isnow being made for integration of communications by permitting voicecommunication on the LAN in addition to a conventional telephone network(including a PBX network that is a private branch exchange network.

As an example of such an attempt, there is a "communication system" asshown in FIG. 4. This voice communication system is composed oftelephones connected to a conventional telephone network, packetcommunication units connected to a packeted speech signal communicationnetwork (referred to hereinafter as a packet communication network), anda communication gateway used to realize mutual connections between thetelephones and the packet communication units. A network carrying such aspeech packet on the LAN described above is an example of the packetcommunication network.

Referring to FIG. 4, the reference numerals 21 and 22 designatetelephones connected to a private branch exchange network (a PBXnetwork) 13 and a public telephone network 20, 104 designates asubscriber line of the private branch exchange network 13, 105designates a subscriber line of the public telephone network 20, andthey have the same interface. On the other hand, the reference numeral101 designates a packeted speech signal transmission network in the formof, for example, a LAN based on the CSMA/CD (carrier sense multipleaccess with collision detection) scheme according to the standardsdefined in the IEEE 802. 3. A plurality of packet communication units14, 15 and 16 are connected to this LAN 101.

The packet communication units 14, 15 and 16 are in the form of smallsize computers, such as, personal computers provided with handsets 17,18 and 19 respectively. These packet communication units 14, 15 and 16have, on one hand, functions of packeting speech signal inputs from thehandsets 17 to 19 and sending out the packeted speech signals onto theLAN 101 and, on the other hand, functions of converting the packetedspeech signals received via the LAN 101 into ordinary voice streamsagain and reproducing the original speech by the handsets 17, 18 and 19.

The reference numeral 11 designates a mail box connected to the LAN 101to store a filed voice mail. The packet communication units 14, 15 and16 can store such filed voice mails in the mail box 11 through the LAN101 and can also fetch such voice mails, transmitted from the otherpacket communication units and stored in the mail box 11, so as tointernally convert the stored voice mails into voice streams again andreproduce the original speech signals by the handsets 17, 18 and 19.

The reference numeral 12 designates a communication gateway whichcontrols communication between the LAN 101 that is the packetcommunication network and the private branch exchange network 13 that isthe conventional telephone network. In this case, a subscriber lineaccommodating an existing telephone is commonly used as a connectionline 102 between the private branch exchange network 13 and thecommunication gateway 12. However, this connection line 102 may be aninterface between the telephones in the private branch exchange network.

Suppose now the case where voice communication is made among the packetcommunication units 14, 15 and 16 in the LAN 101 in the voicecommunication system having the structure described above. In the caseof making voice communication between, for example, the packetcommunication units 14 and 16, the speech packet is transferred througha communication path 121. On the other hand, in the case of makingcommunication between the packet communication unit 14 and the privatebranch exchange network 13 or the telephone 21 or 22 connected to thepublic telephone network 20, the speech packet is transmitted through acommunication path 122 in the LAN 101. In this case, the packeted speechsignal on the LAN 101 is converted by the communication gateway 12 intothe corresponding voice stream before being transferred to the privatebranch exchange network 13 or the public telephone network 20. In thecase of a speech signal transmitted from the side of the private branchexchange network 13 or the public telephone network 20 toward the packetcommunication unit 14 in the LAN 101, its voice stream is packeted bythe communication gateway 12 to be sent out to the LAN 101.

In the case of integration of voice communication in a packetcommunication network in the form including a conventional telephonenetwork, it is an undeniable fact that the number of users having theirtelephones connected to the conventional telephone network is actuallypredominantly large although the number of terminals connected to thepacket communication network is increasing. Therefore, when the desiredintegration of the voice communication is considered, the amount ofcommunication between the telephones connected to the conventionaltelephone network and the terminals connected to the packetcommunication network is expected to considerably increase.

On the other hand, when the future of the packet communication networkis reviewed, an undeniable situation will appear in which the userspossessing their telephones already become new members of the packetcommunication network. For example, although specific users, such as,persons holding administrative positions in a company only possess thepacket communication units in the LAN in the company at present, it isapparent that there will be an increasing tendency of introducing thepacket communication units in future so that all the members of thecompany can possess the packet communication units.

However, the prior art packet communication units connected in thepacket communication network are basically considered to makecommunication in packet form. Thus, the desired integration of the voicecommunication in the form including the conventional telephone networkwill bring forth such a problem that the communication gateway tends tobe overloaded due to concentration of loads, resulting in impossibilityof connection or communication.

Further, when the packet communication unit is newly provided for theuser possessing his telephone already, the same user possesses both thetelephone and the packet communication unit. As a result, the costinevitably increases, and such a problem arises that the user cannotdeal with simultaneous occurrence of a communication request from boththe telephone and the packet communication unit. The same applies alsoto the case where the telephone is newly provided for the user whopossesses the packet communication unit only.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a packetcommunication system which can reliably and economically ensurecommunication between communication units connected in a conventionaltelephone network and those connected in a packet mode network.

Another object of the present invention is to provide a packetcommunication system which is constructed to be accommodated in theprior art network by adding a function of connection to the conventionaltelephone network in addition to the function of connection to thepacket mode network, so as to lighten loads imposed on a communicationgateway, to decrease the amount of materials of an interface circuit orparts for connection to the conventional telephone network, and toreduce the cost of the system.

Still another object of the present invention is to provide a packetcommunication system in which a user possessing his telephone alreadycan transmit speech through his telephone subscriber line possessedalready and which also makes its possible to make voice communicationwith another packet communication unit connected in the packet modenetwork.

Yet another object of the present invention is to provide a packetcommunication system which, when an incoming call arrives at the user'spacket communication unit from another while the user is talking,displays the arrival of the incoming call on a display, so that such acall can be dealt with while the other party does not know the fact.

A further object of the present invention is to provide a packetcommunication system in which a speech or like signal arriving at theuser's packet communication unit from the conventional telephone networkis turned into mail form without the necessity for re-connection of theinput to the communication gateway, so as to shorten the period of timerequired for turning the input into the mail form and also to lightenthe load imposed on the communication gateway.

A still further object of the present invention is to provide a packetcommunication system in which, even in the event of sudden power supplyinterruption, an output unit, such as, an externally located telephoneis used for communication, so that, even when the exclusive user of thepacket communication unit is absent, and the power supply is not turnedon, another person can respond to the input.

The present invention which attains the above objects provides a packetcommunication system making communication between a communication unitconnected in a conventional telephone network and that in a packet modenetwork, in which a function of connection to the conventional telephonenetwork is added to a function of connection to the packet mode network,and means for exclusively selecting the connection network is providedso that, at the time of transmission of a signal from one of thecommunication units to the other, the connection path is selectedaccording to the kind of the network to which the other communicationunit belongs, while, at the time of signal reception, the communicationunit is connected to only one of the conventional telephone network andthe packet mode network. That is, the packet communication systemcomprises packet processor means for converting a speech or likeinformation signal inputted from an input unit (for example, atransmitter microphone of a handset) into the form of a packet totransmit the packet to the packet mode network and converting the packettransmitted from the packet mode network into the original speech orlike information signal stream to reproduce the signal stream by anoutput unit (for example, a receiver of the handset), conventionaltelephone network interface control means for reproducing the speech orlike information signal arrived from the conventional telephone networkby the output unit, and exclusive selection means for exclusivelyselecting only one of the conventional telephone network and the packetmode network in response to the arrival of the input signal.

Thus, in the case of communication between the communication unitconnected in the packet mode network and the communication unit, suchas, the telephone connected in the conventional telephone network, aconnection path is formed between them by the function of connection tothe conventional telephone network. On the other hand, in the case ofcommunication between the communication units in the packet modenetwork, a communication path is formed between them by the function ofconnection to the packet mode network. Therefore, the communicationgateway is utilized only for the communication between the communicationunit (for example, the telephone) connected to the conventionaltelephone network only and the communication unit connected to thepacket mode network only, and concentration of loads on thecommunication gateway is avoided. Thus, even when the number of thecommunication units connected in the conventional telephone network maybe large, information, such as, audio information and/or videoinformation can be reliably communicated between the communication unitsin the conventional telephone network and those in the packet modenetwork.

Further, when the packet communication unit is newly provided for theuser possessing his telephone already connected to the conventionaltelephone network, the sole requirement is to connect the subscribertelephone line to the packet communication system of the presentinvention, so that the telephone can be eliminated, and communication ofinformation, such as, audio information and/or video information can beeconomically attained. When, in this case, information signals aresimultaneously inputted from the communication unit connected in thepacket mode network and that in the conventional telephone network, onlyone of the input signals is connected to the user's communication unit,and a busy tone is issued for the other input signal, so that the userdoes not feel any difficulty in dealing with such a situation.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, and features of the present invention willbecome apparent from the following detailed description of preferredembodiments of the present invention when read in conjunction with thedrawings:

FIG. 1 shows the system structure of an embodiment of the packetcommunication system using the packet communication unit according tothe present invention.

FIG. 2 is a block diagram showing in detail the structure of the packetcommunication unit used in the illustrated embodiment of the presentinvention.

FIGS. 3A and 3B show the structure of the packet communication unitprovided with a connection switching circuit for switching overconnection with an externally located telephone in the event of powersupply interruption.

FIG. 4 shows the structure of one form of a prior art packetcommunication system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail by reference to the drawings.

FIG. 1 shows the system structure of an embodiment of the packetcommunication system using the packet communication unit according tothe present invention, and like reference numerals are used in FIG. 1 todesignate like parts appearing in FIG. 4. Referring to FIG. 1, thereference numeral 30 designates a packet communication unit having afunction of connection to both a conventional telephone network and aLAN 101 that is a packet communication network. The packet communicationunit 30 is provided with a connection path for connection to the LAN 101and a connection interface line 103 for connection to a private branchexchange network 13 that is the conventional telephone network. Theconnection interface line 103 provides the same interface as that forsubscriber lines connected to telephones 21 and 22. The connectioninterface line 103 may be connected to a public telephone network 20instead of the private branch exchange network 13. However, for theconvenience of description, it is supposed herein that the connectioninterface line 103 is connected to the private branch exchange network13.

FIG. 2 shows in detail the structure of the packet communication unit30. The packet communication unit 30 is composed of a processor part 31executing overall control, a display part 32 displaying various kinds ofmessages, for example, arrived messages, scenes, for example, addressinput scenes, etc., viewed by the user for the selection of the otherparty, a keyboard/mouse part 35 inputting information required foroperation, a speech packet processor part 33 processing a speech inputand a speech output to and from a handset 19 so as to transmit andreceive a speech packet to and from the LAN 101, a telephone interfacecontrol part 34 controlling the subscriber line interface of theconventional telephone network, and a switch part 36 switched over toselect whether the speech stream to the handset 19 is to be suppliedfrom the side of the LAN 101 or from the side of the private branchexchange network 13. These parts are interconnected with each other by abus 301.

In response to the signal arrival information supplied from the speechpacket processor part 33 or from the telephone interface control part34, the processor part 31 decides whether the communication unit of theother party is connected to the LAN 101 or to the private branchexchange network 13 and executes processing (for example, the exclusivecontrol of the switch part 36) according to the result of decision. Atthe same time, according to the network to which the communication unitof the other party transmitting the signal is connected, the processorpart 31 instructs the speech packet processor part 33 or the existingtelephone interface control part 34 to originate a call. Also, theprocessor part 31 controls the switch part 36 to control the speechstream to be connected to the handset 19.

The packet communication unit 30 incorporated in this embodiment uses acommunication path 121 when it communicates with, for example, a packetcommunication unit 14 located on the LAN 101, while it uses anothercommunication path 123 when it communicates with the telephones 21 and22 connected to the conventional telephone network. Whether thecommunication unit of the other party is located on the LAN 101 orconnected to the private branch exchange network 13 is decided on thebasis of whether an identifier specifying the communication unit of theother party is a network address or a telephone number. Then, on thebasis of the result of the decision, the packet communication unit 30selects the connection path.

When, for example, the communication unit of the other partytransmitting the call is the telephone 21, the processor part 31identifies according to the telephone number that the communication unitof the other party is connected in the private branch exchange network13, and the dial signal is generated from the telephone interfacecontrol part 34. When, on the other hand, the communication unit of theother party transmitting the signal is the packet communication unit 14,the processor part 31 identifies according to the network address thatthe communication unit of the other party is located on the LAN 101, andthe speech packet processor part 33 transmits the packet including theaddress of the other party. As this network address, the IP (internalprotocol) address, the host name of the packet communication unit or thelike is used. Whether the identifier used for specifying the unittransmitting the signal is the telephone number or the network addressis decided on the basis of the rule for designating the identifier ofthe unit to which the signal is transmitted. Further, when it is sodefined that the signal is transmitted through the communication gateway12 when the identifier of the unit to which the signal is transmittedindicates the value in which the identifier allocated to thecommunication gateway 12 is added to the head of the telephone number,the packet communication unit 30 can communicate through thecommunication gateway 12 with the telephones 21 and 22 connected to theconventional telephone network. The network address or the telephonenumber of the communication unit transmitting the signal is inputtedfrom the keyboard/mouse part 35 and displayed on the display part 32 ofthe packet communication unit 30.

The packet communication unit 14 in the prior art packet communicationnetwork must use the communication path 122 extending through thecommunication gateway 12 when it makes communication with the telephones21 and 22 connected to the conventional telephone network only, as shownin FIG. 4. The practical mode in which the packet communication unit 30is newly introduced to be provided for the user who possesses theexisting telephone already will now be considered. In the case of theillustrated embodiment, a bypass route in the form of the connectioninterface line 103 directly connecting the packet communication unit 30and the telephones 21 and 22 to the private branch exchange network 13is provided as shown in FIG. 1, so that the load imposed on thecommunication gateway 12 can be greatly lightened.

The manner of exclusive control for the communication path in the packetcommunication unit 30 will now be described. The processor part 31 inthe packet communication unit 30 can recognize the state of both of theprivate branch exchange network 13 and the LAN 101 through the speechpacket processor part 33 or the telephone interface control part 34.Therefore, when a speech signal arrives while the packet communicationunit 30 is making communication, that signal is dealt with as in thecase of usual busy mode processing by the exclusive control function.

More concretely, when the packet communication unit 30 starts to makecommunication with the telephone 21 connected to the private branchexchange network 13, the processor part 31 changes over the switch part36 to supply the speech input to the telephone interface control part 34and cuts off the supply of the speech input from the speech packetprocessor part 33. When another speech signal arrives from the otherpacket communication unit 14 under the above situation, the processorpart 31 generates a packet indicating that the packet communication unit30 is now busy, and this packet is transmitted from the speech packetprocessor part 33 to the signal transmitting packet communication unit14 through the LAN 101.

On the other hand, when the packet communication unit 30 starts to makecommunication with the other packet communication unit 14 connected tothe LAN 101, the processor part 31 changes over the switch part 36 tosupply the speech input to the speech packet processor part 33 and cutsoff the supply of the speech input from the telephone interface controlpart 34. When another speech signal arrives from the telephone 21connected to the private branch exchange network 13 under the abovesituation, the processor part 31 instructs the telephone interfacecontrol part 34 to generate a busy tone signal, and this signal istransmitted to the signal transmitting telephone 21 through theconnection interface line 103 and the private branch exchange network13.

The packet communication unit 30 operates to effect the above manner ofexclusive control for a speech signal that arrives during communication,so that the user of the packet communication unit 30 is required torespond to the signal arriving from one of the networks only and is thusfreed from such a situation in which he is embarrassed with simultaneousarrival of speech signals from both the networks. When a speech signalarrives during communication by the packet communication unit 30, theprocessor part 31 displays the arrival of the signal on the display part32. In this case, the switch part 36 may be changed over by the user whoviewed and confirmed the display on the display part 32.

The voice mail transfer function will now be described. When a speechsignal transmitted from, for example, the telephone 21 to the packetcommunication unit 30 through the private branch exchange network 13 isprocessed to be received as a speech mail due to, for example, theabsence of the user of the packet communication unit 30, the speechsignal received through the connection interface line 103 is turned intothe speech file by the speech packet processor part 33 and is thentransferred through the LAN 101 to a mail box 11 to be stored as themail whose destination is the user's packet communication unit 30. Thus,as in the case of an automatic answering telephone set, the speechsignal arrived during the period of absence of the user of the packetcommunication unit 30 can be reproduced at any desired later time, sothat the processing required for turning the speech signal into thespeech mail via the communication gateway 12 is now unnecessary, and theperiod of time required for the processing can be shortened togetherwith lightening of the load on the communication gateway 12.

How to bypass the speech signal to an externally located telephone inthe event of interruption of the power supply to the packetcommunication unit 30 will now be described by reference to FIGS. 3A and3B. In FIGS. 3A and 3B, the reference numeral 40 designates a packetcommunication unit exhibiting a bypass function in the event of powersupply interruption or down, 45 designates a control part having afunction similar to that of the packet communication unit 30 shown inFIG. 2, 41 designates an externally located telephone, and 42 designatesa handset of the telephone 41. The externally located telephone 41 has apower supply different from that for the packet communication unit 40.The reference numerals 43 and 44 designate relay contacts switched overunder control of the processor part 31 shown in FIG. 2. More concretely,under the state in which the power supply for the packet communicationunit 40 is not turned on, the relay contact 44 is switched over to theposition where the connection interface line 103 is connected to theline terminal of the telephone 41 as shown in FIG. 3A, while the relaycontact 43 is switched over to the position where the handset 42 isconnected to the handset terminal of the telephone 41.

On the other hand, under the state in which the power supply for thepacket communication unit 40 is turned on, the relay contact 44 isswitched over to the position where the connection interface line 103 isconnected to the line terminal of the telephone interface control part34 shown in FIG. 2 and included in the control part 45 as shown in FIG.3B, while the relay contact 43 is switched over to the position wherethe handset 42 is connected to the handset terminal of the switch part36 shown in FIG. 2 and included in the control part 45.

By the above manner of bypass control, the externally located telephone41 can be used to secure the speech even in the event of interruption ofthe power supply to the packet communication unit 40. The function ofthe externally located telephone 41 can be built in the packetcommunication unit 40 when the circuit is designed to utilize the powerfed from the telephone exchange equipment.

The packet transmitted to and received from the LAN 101 in theembodiments described above may be any one of a packet having a variablelength and that having a fixed length.

Although the above embodiments have been described by reference to thecase where a speech signal is transmitted and received, it is apparentthat the present invention is also applicable to the case oftransmission and reception of a video signal or an image signal. Thus, avideo telephone or the like can be connected to the conventionaltelephone network. In the case of transmission and reception of a videosignal or an image signal, the display part 32 functions as the outputunit, while an image input unit, such as, a television camera connectedin place of the transmitter microphone of the handset functions as theinput unit.

I claim:
 1. A packet communication system for making communicationbetween a communication unit connected in a conventional telephonenetwork and a communication unit connected in a packet mode network,comprising:means for connecting said communication unit connected in apacket mode network to said conventional telephone network; means forconnecting said communication unit connected in a conventional telephonenetwork to said packet mode network; an input unit for inputting anexternal information signal from an external source; an output unit forreproducing an information signal and outputting the reproducedinformation signal; packet processor means for converting said externalinformation signal inputted from said input unit into the form of apacket transmitting the packet to said packet mode network andconverting the packet transmitted from said packet mode network into aninformation signal and providing the information signal to said outputunit; conventional telephone network interface control means forreproducing by said output unit an information signal received from saidconventional telephone network; and exclusive selection means forselectively operating one of said conventional telephone networkinterface control means and said packet processor means in accordancewith whether the information signal arrives from said packet modenetwork or from said conventional telephone network.
 2. A packetcommunication system according to claim 1, further comprising means forselecting either said conventional telephone network interface controlmeans or said packet processor means at the time of signal transmissionon the basis of the information of the destination of the signaltransmission.
 3. A packet communication system according to claim 1,further comprising mail formatting means for converting the informationsignal received from said conventional telephone network into the formof the packet and transferring the packet to a mail server connected tosaid packet mode network to store the same.
 4. A packet communicationsystem according to claim 1, further comprising control means forconnecting the information signal received from said conventionaltelephone network to an additional output unit different from saidoutput unit and having a power supply different from that for saidpacket communication unit when the power supply for said packetcommunication unit is not turned on.
 5. A packet communication systemaccording to claim 1, wherein said packet communication unit isconnected to said conventional telephone network through said packetmode network and a communication gateway.
 6. A packet communicationsystem according to claim 1, wherein said packet communication unitincludes at least a display unit as said output unit, and arrival ofsaid information signal is displayed on the screen of said display unit.7. A packet communication system according to claim 1, wherein saidinformation signal includes an audio signal.
 8. A packet communicationsystem according to claim 1, wherein said information signal includes avideo signal.
 9. A packet mode network system for making communicationwith a communication unit connected in a conventional telephone network,comprising:a packet mode network for transmitting a packet, and aplurality of packet communication units connected to said packet modenetwork; at least one of said plural packet communication units beingconnected to said conventional telephone network; an input unit forinputting an information signal from an external source; an output unitfor reproducing an information signal and outputting the same; packetprocessor means for converting said information signal inputted fromsaid input unit into the form of a packet to transmit the packet to saidpacket mode network and converting the packet received from said packetmode network into an information signal and providing the informationsignal to said output unit; conventional telephone network interfacecontrol means for reproducing by said output unit an information signalreceived from said conventional telephone network; and exclusiveselection means for selectively operating only one of said conventionaltelephone network interface control means and said packet processormeans according to whether the information signal arrives from saidpacket mode network or from said conventional telephone network.
 10. Apacket mode network system according to claim 9, wherein said packetcommunication unit connected to said conventional telephone networkfurther includes means for selecting at the time of signal transmissionone of said conventional telephone network interface control means andsaid packet processor means on the basis of the information of thedestination of the signal transmission.
 11. A packet mode network systemaccording to claim 9, wherein said system further comprises a mailserver connected to said packet mode network, and said packetcommunication unit connected to said conventional telephone networkfurther includes mailing means for converting the information signalreceived from said conventional telephone network into the form of thepacket and transferring the packet to said mail server to store thesame.
 12. A packet mode network system according to claim 9, whereinsaid packet communication unit connected to said conventional telephonenetwork further includes control means for connecting the informationsignal received from said conventional telephone network to anadditional output unit different from said output unit and having apower supply different from that for said packet communication unit whenthe power supply for said packet communication unit is not turned on.13. A packet mode network system according to claim
 9. wherein saidpacket mode network system is connected to said conventional telephonenetwork through a communication gateway.
 14. A packet mode networksystem according to claim 9, wherein said information signal includes anaudio signal.
 15. A packet mode network system according to claim 9,wherein said information signal includes a video signal.
 16. A packetmode network system for making communication with a communication unitconnected in a conventional telephone network, comprising:a packet modenetwork for transmitting a packet, and a plurality of packetcommunication units connected to said packet mode network; at least oneof said plural packet communication units being connected to saidconventional telephone network; an audio input unit for inputting anaudio signal from an external source; an audio output unit forreproducing an audio signal and outputting the same; a video input unitfor inputting a video signal from an external source; a video outputunit for reproducing a video signal and outputting the same; packetprocessor means for converting an information signal including the audiosignal inputted from said audio input unit and the video signal inputtedfrom said video input unit into the form of a packet and transmittingthe packet to said packet mode network and converting the packettransmitted from said packet mode network into an information signalstream and providing the information signal stream to both said audiooutput unit and said video output unit; conventional telephone networkinterface control means for reproducing an information signal receivedfrom said conventional telephone network by both said audio output unitand said video output unit; and exclusive selection means forselectively operating only one of said conventional telephone networkinterface control means and said packet processor means according towhether the information signal arrives from said packet mode network orfrom said conventional telephone network.
 17. A packet mode networksystem according to claim 16, wherein said packet communication unitconnected to said conventional telephone network system further includesmeans for selecting at the time of signal transmission one of saidconventional telephone network interface control means and said packetprocessor means on the basis of the destination of the signaltransmission.
 18. A packet mode network system according to claim 17,wherein said packet communication unit connected to said conventionaltelephone network displays the arrival of the information signal on thescreen of said video output unit.